The man, who has not been identified, blew up one of the bombs by throwing it onto a bonfire.
He took the other six mortar bombs to his home in the western Kaliningrad Region, RIA Novosti reported.
Police posed as potential purchasers of the explosives and later detained the man.
The 29-year-old suspect is unemployed and has previous drug dealing convictions, police said.
2014: The Year in Music [PHOTOS]